Chafee spokesman Christian Varieka told WPRI.com the governor will make his announcement at 10:30 a.m. Thursday at Warwick City Hall. (Yes, Varieka made the call on personal time.) The news – first broken hundreds of miles south of Rhode Island by Politico and The Washington Post – struck the state’s political class like a thunderbolt Wednesday, despite the fact that Chafee has long indicated he was open to the possibility and amid rising speculation the move was coming.

Ideologically speaking, the switch makes perfect sense: Chafee is more aligned with the national Democratic Party than many of its nominal officeholders in Rhode Island. Think about it: this is a governor elected with the support of the state’s teachers’ unions on a platform of raising taxes to fund social services who just signed a law legalizing same-sex marriage in the nation’s most Catholic state.

Politically, Chafee has been a Democrat in all but name for a long time now – in 2012 he not only co-chaired President Obama’s re-election campaign and spoke at the Democratic National Convention, he even endorsed Sheldon Whitehouse’s bid for the very U.S. Senate seat he took from Chafee in 2006.

Clearly, Chafee and his savvy chief of staff, former Patrick Kennedy aide George Zainyeh, decided the approval-challenged governor’s best bet for a second term was in the Democratic Party. (Indeed, Chafee’s 2011 decision to replace the more Republican-friendly Pat Rogers with Zainyeh now seems telling.) But what’s the path? And are they right? Here are a few initial thoughts.

The best evidence available is Public Policy Polling’s January survey, which tested a wide variety of 2014 scenarios. Chafee won the biggest share of voters – 35% – as the Democratic candidate in a three-way race against Republican Brendan Doherty (who’s not running) and Moderate Party candidate Ken Block (who is), suggesting the governor’s ceiling of support remains about where it was in 2010 if he runs as a Democrat; as an independent, by contrast, he got 23% at most.

Now that Chafee is running as a Democrat, though, there’s no guarantee he’ll make it onto the November ballot, because he may have to beat Treasurer Gina Raimondo and Providence Mayor Angel Taveras in a primary.

Chafee will have real advantages in the primary, not least of them the support of Barack Obama, who pronounced himself “delighted” at the decision in a statement Wednesday. Even if the president declines to make a formal gubernatorial endorsement, his tacit support is no small thing in a state that twice voted 63% for him.

“For nearly 30 years, Linc Chafee has served his beloved Rhode Island as an independent thinker and leader who’s unafraid to reach across party lines to get things done,” the president said, adding: “I’m thrilled to welcome Linc to the party of Jefferson and Jackson, Roosevelt and Kennedy – and I look forward to working with him in the years ahead.”

Vt. Gov. Peter Shumlin, chairman of the Democratic Governors Association, is friendly with Chafee, too, and publicly encouraged him to join the party earlier this year. But he wasn’t exactly full-throated in his backing for Chafee on Wednesday.

“We are excited to welcome Governor Chafee to the ranks of Democratic governors and look forward to enthusiastically supporting whoever emerges as the Democratic nominee in Rhode Island,” Shumlin said in a short statement, which pointedly did not endorse the incumbent.

Closer to home, Chafee is also a better fit for Congressman David Cicilline, a key Democratic powerbroker, than either Raimondo or Taveras. Joining the party should help Chafee with fundraising (who also has the backstop of his family fortune). And as mentioned earlier, his policy positions will appeal to many base Democrats.

“If you look at the governor’s principles and priorities throughout his career in public offices from his time as mayor of Warwick and a Warwick city councilman, in the United States Senate and through his first two years as governor, his principles and priorities align well with those of the Democratic Party,” Varieka said.

Adding Chafee to the primary scrambles the calculations for both Raimondo and Taveras, each of whom would now be mounting a primary challenge against the incumbent Democratic governor rather than competing in an open field. The PPP poll showed Raimondo holding a 13-point lead over Chafee among primary voters, with Taveras a close third. Chafee would presumably be seeking support from the same liberal and union voters that Taveras needs to win: the PPP poll found that Taveras’s support nearly doubled with Chafee out of the primary, shaving Raimondo’s lead to 9 points. Former Auditor General Ernie Almonte, who’s now left the race, also got around 10% support in the PPP poll.

Will Taveras still run? The mayor, who has the highest approval rating in Rhode Island, faces perhaps the hardest choice among the three. Although he’d likely win a second City Hall term in a landslide, and he gets along well with Chafee, he’s already fundraising and staffing up for a gubernatorial bid. Providence’s corner office is a place where higher aspirations go to die, and Taveras may not want to risk another four years. He could try to put together a winning coalition against Chafee and Raimondo based off his successes in Providence, his natural appeal to Rhode Island’s fast-growing Latino electorate and his conciliatory approach to pensions.

Taveras tweaked Chafee – gently – in a statement released Wednesday. “I have been a Democrat and a Red Sox fan my whole life, and I don’t intend on changing either,” the mayor said. “I remain focused on bringing people together to make necessary but difficult decisions that will move our city and state forward.”

For Raimondo, Chafee’s new affiliation presents challenges and opportunities. The challenge is facing a well-funded and well-known opponent who’s more associated with Democratic priorities than she is, someone with national connections who may get the backing of public-sector unions seeking to block her rise. (Then again, those same unions’ rank-and-file members may not forget that Chafee signed the pension law Raimondo designed.) The opportunity for the treasurer is having the governor and the mayor split the liberal-labor-Latino coalition and, if she sees them off, avoiding a four-way general election.

Unsurprisingly in light of their frosty relationship, Raimondo’s reaction to Chafee’s announcement was chillier than Taveras’s. “As I have said before, I am seriously considering running for governor,” she said. “The question Rhode Islanders have is who can provide the leadership we need to move our state forward.”

Raimondo added, bitingly: “The governor’s decision to change parties for a second time has not changed my thinking.”

Speaking of the general election, one of the biggest beneficiaries from Chafee’s decision may be Cranston Mayor Allan Fung, the likely Republican nominee, who looks unlikely to face a primary challenger.

Remember that Democrats have lost eight of Rhode Island’s last 10 gubernatorial elections – Bruce Sundlun won in 1990 and 1992 – and as recently as three years ago a virtually unknown GOP candidate, John Robitaille, came within 9,000 votes of beating Chafee. Rhode Islanders aren’t going to back a Republican presidential candidate anytime soon, but they have no problem pulling the lever for a GOP governor.

With Ken Block taking perhaps 5% to 10% of the vote for his nascent Moderate Party, Fung or the Democratic nominee will need less than 50% to win. A primary could leave the Democrat battered, with Fung waiting in the wings after husbanding money for the final two months. If Chafee manages to win the primary, he will need to prove he can get his support above 40%; if one of the other two Democrats emerges the winner, Fung can fight them on the Republican-friendly turf of fiscal conservatism and good management.